Roll assembly



April 1969 s. R. RACKOFF ETAL 3,435,499

ROLL AS 5 EMBLY Sheet of Filed Dec. 22, 1967 6.!25 ioo| 50o" RADIUSFIG.4

*1 IHO INVENTORS SELWYN R. RACKOF F MARTIN J.DEMPSEY A TTORNE Y April1969 s. R. RACKOFF ETAL 3,435,499

ROLL AS SEMBLY Filed Dec. 22, 1967 Sheet 2 of 2 F IG.6

United States Patent 3,435,499 ROLL ASSEMBLY Selwyn R. Rackoif andMartin J. Dempsey, Bethel Park,

Pa., assignors to American Shear Knife Co., West Homestead, Pa, acorporation of Pennsylvania Filed Dec. 22, 1967, Ser. No. 692,785 Int.Cl. B21k 1/02; B21b 31/08; B2311 11/02 US, Cl. 29-425 8 Claims ABSTRACTOF THE DISCLOSURE A roll assembly including a tungsten-carbide rollinsert on a mandrel having a flange engaged by a lateral surface of theroll. The engaging surface of the insert is roughened by adheredparticles of tungsten carbide and the roller is compressed against theflange so that the particles bite into the flange. To reduce tensilestress on the tungsten-carbide insert the inside diameter of the insertand the outside diameter of the mandrel are made equal and the insert ismounted by cooling the mandrel and slipping the insert over the mandrel.

Background of the invention This invention relates to the art ofreducing work by rolling and has particular relationship to thereduction of work by rolling with rolls of materials or metalloids ofthe tungsten-carbide type. The expression of the tungsten-carbide typeas used in this application means primarily tungsten carbide (WC) andits alloys. It also means other hard metalloids such as titaniumcarbide, molybdenum carbide, tantalum carbide, niobium carbide andnumerous others including borides, silicides, nitrides, and the like,and their alloys. For an elaborate list of these metalloids reference ismade to Goetzel 2,581,252, particularly column 6, beginning line 16.

In the interest of concreteness this invention is discussed in thisapplication with reference to the rolling or reduction of Billets to rodor rod to wire. The reduction of rod is carried out by oppositelyengaging the reducing rolls of a pair of roll assemblies in reducingrelationship with the rod while rotating the assemblies and advancingthe rod.

Typically, steel is reduced to round wire of about .218" to .5625"diameter and the wire is delivered at the rate of 5000 to 10,000 feetper minute (typically 8500 f.p.m.) from a 25-stand system. In the highnumbered stands (from the 17th) the roller assemblies rotate at about1600 revolutions per minute. The reducing rolls particularly in theadvanced assemblies are of the tungsten-carbide type. In each rollassembly including a roll of the tungsten carbide type, the roll is inthe form of an annular insert and is mounted on a mandrel of steel,which is driven to produce the rolling operation. During the rollingtperation the roll insert is subjected to enormous stresses and it isnecessary that rotation of the insert relative to the mandrel beprevented.

In accordance with prior-art practice the tungsten-carbide roll isprovided with precisely dimensioned keys which are locked to suppressrelative rotation of the roll and mandrel. In addition the insidediameter of the roll is dimensioned substantially smaller than theoutside diameter of the mandrel (so that there will be no relativemovement in use). A high failure-rate of rolls in these prior-artassemblies has been experienced. In addition these prior-art assembliesare difiicultand costly to produce because of the precise dimensioningof the keys in tungsten-carbide which is not readily worked. There isalso a high-failure rate of the rolls during production so that theproduction shrinkage is high.

3,435,499 Patented Apr. 1, 1969 It is an object of this invention toovercome the above described disadvantages of the prior-art rollassemblies, and to produce assemblies which shall be producible at arelatively lower cost than prior-art assemblies and shall not fail at ahigh rate in the making or in use and also to provide a method ofproducing such assemblies.

Summary of the invention This invention arises from the realization thatthe high rate of failure of the rolls in prior-art assemblies, both whenthey are made and later, is caused by the keys and by the manner inwhich the assemblies are made. The keys are in effect notched regionsand their very presence weakens the rolls. In addition the dimensioningof the inside diameter of the roll smaller than the outside diameter ofthe mandrel causes enormous tensional forces to be applied to the rollby the mandrel as it warms up during the making of the assembly andcauses the roll to fail during making, or, in its weakened condition,shortly after the assembly is put into use. It is an object of thisinvention to provide an assembly in which the roll insert is a smoothannulus but the roll assembly is accomplished in such a way that theroll insert does not have a high rate of failure and does not, when inuse, move relative to the mandrel.

In accordance with this invention a roll assembly is provided in whichthe roll is a smooth annulus but its lateral face or surface whichengages the flange of the mandrel is roughened. The roughening iseffected by securing or binding to this face a hard particled material,typically particles of the tungsten-carbide type mixed with a brazingmaterial such as copper. Typically the particles are of -30 to +20 mesh,but they may be smaller, even a powder. To roughen a later face of aroll insert the particles of tungsten-carbide and brazing material aredisposed on the surface and then the surface is raised to the sinteringtemperature of the carbide. This temperature exceeds the brazingtemperature of the brazing material and the particles are joined to thesurface both by sintering and brazing. Alternatively, the brazingmaterial alone may serve to hold the particles on the surface.

The tensional forces which disrupt the roll inserts of prior-artassemblies is, in the practice of this invention, reduced bydimensioning the inside diameter of the insert and the outside diameterof the mandrel substantially equal. The mandrel is then cooled and theroll insert slipped over it and compressed by a pressure exerting tonsof force. A nut is then screwed onto the mandrel. The nut engages theremaining face of the insert and has grooves which are engaged by aspanner wrench and the wrench is turned to exert additional compressiveforce on the insert. The mandrel is then provided with additionalgrooves coextensive with the grooves in the nut to provide a keywaywhich serves in the use of the assembly.

The mandrel, nut and insert are coordinated in strength. The mandrel andnut are hardened typically, to 50 to 55 Rockwell-C hardness. The groovesin the mandrel may be cut out in various ways but are typically cut outby abrasive sawing.

Brief description of the drawings For a better understanding of thisinvention, both as to its organization and as to its method ofoperation, together with additional objects and advantages thereof,reference is made to the following description, taken in connection withthe accompanying drawings, in which:

FIGURE 1 is a plan view of a roll assembly constituting an embodiment ofthis invention;

FIG. 2 is a view in section taken along line IIII of FIG. 1;

FIG. 3 is a plan view of the roll insert of the assembly shown in FIG.1;

FIG. 4 is a view in section taken along line IV-IV of FIG. 3;

FIG. 5 is a fragmental view enlarged showing the relationship betweenthe roll and the flange and the roughening interposed between the rolland flange; and

FIGS. 6 and 7 are views showing typical dimensions of the mandrel, andinsert included, not with any intention of limiting this invention inany way, but with the purpose of aiding those skilled in the art topractice this invention.

Description preferred embodiment The apparatus shown in the drawingsincludes a roll assembly A having a mandrel M, a roll insert R of thetungsten-carbide type and a nut N. The roll insert is held tightly,against relative rotation under the high stresses, between the nut N andthe flange F of the mandrel M. An aspect of this invention resides inthe prevention of relative rotation by the provision in the surface S ofthe carbide roll R, which engages the flange F, of a rough surface whichbites into the surface of the flange F. It is not obvious that a surfaceof tungsten carbide, a very hard material, can be roughened so that itwill hold under the high stresses to which the roll is subjected. Butoperation has shown that the assembly according to this invention doeshold. The roughened surface S may typically be provided as follows:

A mixture of copper powder or particles (or other brazing material) andtungsten-carbide powder or particles is deposited on the surface of thepresintered roll to be roughened. The roll is then heated to thetungsten-carbide sintering temperature which is higher than the brazingtemperature for the copper. The tungsten carbide is brazed and sinteredto the roll. In the sintering the cobalt of the roll material fuses tothe tungsten-carbide particles so that the particles become part of theroll surface. The tungsten carbide powder consists of small tetrahedra T(FIG. which are sintered to the roll insert surface on their bases withtheir sharp apices outwardly.

The mandrel M is composed of very hard tool steel. The outer diameter ofthe mandrel is dimensioned precisely (typically within :0001 inch) equalto the inside diameter of the roll insert (compare FIGS. 6 and 7). Themandrel M is cooled to about 150 F. and the roll R is then slipped overthe mandrel M. The roll R is then compressed onto the mandrel byapplying about 160 tons force or higher (typically 300 tons) to theroll. The

nut N is then screwed on and tightened by engaging a t long spannerwrench in the grooves G (see FIGS. 1 and 2). Substantial compressiveforce is applied between the surfaces, S, of the roll R and flange F inthis way. The portion of the mandrel M bounded by the grooves G is thensawed out by an abrasive saw and the slot through the grooves G and theadjacent portion of the mandrel M serves as a key slot in which adriving key K engages in the use of the apparatus. Movement of the nut Nrelative 4: to the mandrel M is thus prevented. The equal dimensioningof the mandrel outside diameter and the roll inside diameter reduces thetensile stress to which the roll is subject during subsequent use, whenthe roll temperature at the work may be as high as 1600 F. to 2000 F.,so

that the roll failures are minimized.

What is claimed is:

1. A roll assembly including a cylindrical mandrel having a flange and aroll insert of the tungsten-carbide type on said mandrel, said inserthaving a lateral surface, means connected to said insert for holdingsaid lateral surface in firm engagement with said flange, said lateralsurface being roughened so that it bites into said flange and is heldagainst rotation by said flange, the roughening on the lateral surfacebeing a mixture of particles of the tungsten carbide type and of abrazing material.

2. The assembly of claim 1 wherein the brazing material is copper.

3. The assembly of claim 1 wherein the particles of thetungsten-carbidetype are adhered to the lateral surface.

4. A roll assembly including a cylindrical mandrel, a flange of metal onsaid mandrel, a roll insert of the tungsten-carbide type on saidmandrel, said insert having a lateral surface, means engaging saidinsert for forcing said lateral surface into firm engagement with saidflange, and adhesive means interposed between said lateral surface andsaid flange, said adhesive means being of a type which is capable ofbiting into the material of said flange and when actuated by saidforcing means so biting into said flange and effectively holding saidinsert against rotation on said mandrel.

5. The assembly of claim 4 wherein the adhesive means is a roughening onthe lateral surface and the lateral surface is forced into engagementwith the flange under high compressive pressure so that the rougheningeflectively bites into the flange.

6. The assembly of claim 4 including a key through the forcing means andthe mandrel for preventing rotation of the forcing means relative to themandrel.

7. The assembly of claim 4 wherein the adhesive means consists ofparticles of the tungsten carbide type sintered to the lateral surface.

8. The assembly of claim 4 wherein the flange is composed of hardenedalloy steel and the adhesive means is composed of particles of thetungsten-carbide type capable of biting into the flange when the lateralsurface is held in firm engagement with the flange.

References Cited UNITED STATES PATENTS BILLY I. WILHITE, PrimaryExaminer.

- US. Cl. X.R. 29148.4, 447

